Several vacuum cleaners are known in the art, both for domestic use and for industrial use. They typically have a body which houses internally a motor unit which produces the suction effect, a filter unit situated ahead of the motor and an element for collecting the sucked-up material in the form of a collector chamber or a bag.
Typically, the motor unit is connected to the exterior of the body by means of a tube which has one end engaged inside an opening provided in the body and an opposite end which terminates in a mouth on which various accessories may be alternately fitted in order to adapt the sucking action to the surfaces to be treated.
These accessories include suction cleaner nozzles. A suction cleaner nozzle typically comprises a housing which is provided in the upper zone with an engaging opening for the mouth of the tube. The housing houses a rotatable drum which has peripherally a plurality of bristles distributed in a predefined arrangement and intended to brush the surface to be treated and conveying the collected material towards the opening and thus towards the tube. The drum provided with the plurality of bristles is also termed rotatable brush.
Rotation of the rotatable brush can be performed in various ways.
According to a first solution, the housing has, mounted inside it, an electric motor having, projecting therefrom, a rotatable shaft which is connected, for example by means of an endlessly wound drive belt, to the rotatable brush so as to transmit a rotational movement to the rotatable brush.
Powering of the electric motor may be performed by means of the power line or by means of batteries.
According to a second known solution, rotation of the rotatable brush is performed by means of a turbine which is mounted opposite the opening of the housing.
The suction action produced by the motor unit generates an air flow conveyed towards the turbine which causes rotation thereof. The turbine is connected to the rotatable brush by means of an endlessly wound drive belt and transmits the rotational movement to the rotatable brush.
The known solutions for powering the electrical motor have certain drawbacks.
A first drawback is that the electric power supply from the power line requires a connection between the latter and the electric motor by means of electric cables which, therefore, hinder the user during use of the vacuum cleaner.
Another drawback is that powering by means of batteries requires cyclical recharging of the latter, during which the vacuum cleaner nozzle cannot be used; moreover, the batteries require an expensive and cumbersome recharging equipment.
A further drawback is that powering by means of turbines moved by the suction air flow supplies a substantially low rotational torque to the drum: this causes in given circumstances, for example, during use of the vacuum cleaner on rugs or carpets with long pile, a substantial reduction in the speed of rotation of the rotatable brush. In some cases, the speed is reduced to the point of seizing thereof, owing to the strong adhesion or possible intertwining which occurs between the bristles and the pile of the surface being treated and with a consequent substantial reduction in the suction efficiency.